What is the Difference Between Allylic and Vinylic Carbons?

The main difference between allylic and vinylic carbon lies in their connection to a double bond and their hybridization. Here are the key distinctions:

1. Connection to a double bond: Vinylic carbon is one of the two atoms that form (or share) the double bond, while allylic carbon is the carbon atom that is next to the double-bonded carbon atom. In other words, vinylic carbon is directly involved in a double bond, whereas allylic carbon is indirectly related to a double bond.
2. Hybridization: Vinylic carbon is sp2 hybridized, as it forms a double covalent bond. On the other hand, allylic carbon is sp3 hybridized, as it forms a single covalent bond.
3. Bond Length: The C-H bond length in allylic carbon is higher, while the vinylic C=H bond is shorter.
4. Bond Type: Allylic carbon only forms a single bond, whereas vinylic carbon can have either two double bonds in its sides or one double bond, and it forms at least one double bond.
5. Number of Hydrogen Atoms: Vinylic carbon can be bonded to other carbons via double bonds from its both sides, and then all three carbon atoms are called vinylic carbons. In contrast, allylic carbon is bonded to a carbon atom that in turn is doubly bonded to another carbon atom.

In summary, vinylic carbon is directly involved in a double bond and is sp2 hybridized, while allylic carbon is indirectly related to a double bond and is sp3 hybridized. These differences in connection to a double bond and hybridization result in distinct chemical properties for allylic and vinylic carbons.

Comparative Table: Allylic vs Vinylic Carbons

The main difference between allylic and vinylic carbons lies in their connection to a double bond in a molecular structure. Here is a comparison table highlighting the key differences between allylic and vinylic carbons:

In summary, allylic carbon is connected to a double-bonded carbon atom through a single bond, while vinylic carbon is directly involved in a double bond with another carbon atom. Allylic carbon is sp³ hybridized, and vinylic carbon is sp² hybridized.